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5. Genes are the sections of DNA on
chromosomes that control traits.
6. Alleles are different forms of a gene pair.
Each one of the pair is an allele.
Each organism inherits a combination of two
alleles - one from each parent.
**Individual alleles control the inheritance of
traits. Some are dominant and others are
recessive.
7. A dominant allele is one
whose trait always shows up in
the organism when the allele is
present. It blocks another
genetic factor. Ex. Dimples
8. A recessive allele is
blocked or covered up,
whenever the dominant allele
is present.
Ex. No dimples
Dominant and recessive traits are represented by
using letters.
9. Dominant traits are represented by capital letters.
10.Recessive traits are represented by lower case
letters.
Example: B = brown hair
b = red hair
BB = brown hair / purebred
Bb = brown hair / hybrid
bb = red hair
/ purebred
11.Purebred (True-bred)—An organism
that always produces offspring with the
same form of a trait as the parent. Also
known as homozygous.
Example: Purebred blonde haired parents will always
have blonde haired children.
12. In Mendel’s experiments,
P stood for the parent generation,
F1 stood for the first generation, and
F2 stood for the second generation.
13.Hybrid—An organism that has two
different alleles for a trait. ALSO known as
heterozygous.
14.Homozygous—an organism that has 2
identical alleles for a trait
Example– BB – homozygous for brown hair
bb – homozygous for red hair
15.Heterozygous—an organism that has two
different alleles for a trait
Example – Bb – heterozygous for brown hair
16.Phenotype—physical make-up of an
organism
***you can actually see phenotype***
Ex. -- Tall and short.
17.Genotype—genetic make-up of an organism
***you cannot see genotype***
Ex. -- BB,
Bb,
bb
Punnett Square—A chart used in
genetics to show all the possible
combinations of alleles.
Chromosomes are:
• located inside the nucleus of cells.
• made of DNA which carries genetic
information from parent to offspring.
Humans have 46 total chromosomes.
• 23 in each sex cell.
Grasshoppers have 24 chromosomes.
• 12 in each sex cell.
Dogs have 78 chromosomes.
• 39 in each sex cell.
House flies have 12 chromosomes.
6 in each sex cell.
DNA is the genetic material that carries
information about an organism and is
passed from parent to offspring.
Gene: a segment of DNA on
a chromosome
that codes for a specific trait.
Meiosis: the process by which the
number of chromosomes is reduced
by half to form sex cells.
sperm from the male
egg from the female.
During meiosis:
1. the chromosome pairs separate, and
are distributed to four different cells.
The resulting sex cells have only half as
many chromosomes as the other cells in the
organism.
Each gene pair
has an allele
from mom and
an allele from
Dad.
You have 23 pairs of chromosomes per cell.
Each parent contributes one half of the pair.
Each chromosome contains thousands of genes.
MUTATION
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Pedigrees
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Selective Breeding
Selective breeding is the process
of selecting a few organisms
with desired traits to serve as
parents of the next generation.
People use selective breeding to
increase the value of plants or
animals, such as fruits or
vegetables or dairy cows.
Examples of selective breeding:
Inbreeding – crossing two parents that
have identical or similar sets of
alleles.
Ex: Purebred horses with
exceptional speed are crossed to
produce offspring to run very fast.
Purebred dogs are crossed to
maintain hunting skills.
2. Hybridization – the crossing of
two genetically different parents for
getting the best traits from both
parents.
Ex: Farmers cross the corn that
have the sweetest kernels with a
parent that is disease resistant.
3. Cloning - A clone is an organism
that is genetically identical to the
organism from which it is produced.
Example : A cutting from a plant that
grows a new plant is genetically identical
to the mother plant.
Advantages and
Disadvantages of
Purebreds
&include:
Hybrids
Purebred
advantages
1. Working animals perform better
2. Food animals produce better tasting foods
3. Plants may have higher yields
4. Plants may have better tasting foods
Purebred disadvantages may include:
1.
Inbreeding increased the probability of
genetic disorders
2.
Purebred species are more expensive
3.
Plants may produce unattractive foods
4.
Plants may not have disease resistance
Hybrid advantages include:
1. Food animals able to produce more food
2. Plants may have higher disease resistances
3. Plants may have more “curb appeal”
(attractive appearance, better shipping, etc.)
4. Animals may have larger litters and better
survival rates for the young
Hybrid disadvantages include:
1. May not always get the desired trait
2. May be more expensive to produce & seeds
may not always have high viability
3. May not taste as good as purebred
Genetic Engineering is the transfer of genes
from one organism into the DNA of another
organism. This is also called “gene splicing.”
because the DNA molecule is cut open and a
gene is “spliced “ into it. Usually involves bacteria.
It can produce medicines such as insulin for
diabetics.
It can improve food crops by making them
more tolerant to certain conditions – drought,
frost,
It may be used one day to replace genes for
curing genetic diseases.